Mechanical Ventilation

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  1. Spontaneous Breathing
    the movement of air into and out of the lungs
  2. Pawo and Paw
    Mouth or airway opening pressure
  3. Air will always move from the...
    High pressure point to the low pressure point
  4. During spontaneous inspiration...
    The pressure in the alveoli becomes less than the pressure at the airway opening and gas flows into the lungs
  5. During spontaneous Expiration..
    Gas flows out of the lungs because the pressure in the alveoli is higher than the pressure at the airway opening
  6. The pressure at the body surface!
    Is equal to zero (atomospheric pressure)
  7. Inteapleural pressure
    Is the pressure in the potential space between the parietal and visceral pleurae
  8. Pbs
    Pressure at the body surface
  9. Ppl
    Intraplueral pressure
  10. Intrapleural pressure (Ppl) is normally what at the end of expiration?
    -5 cm H2O
  11. Intrapleural pressure (Ppl) is normally what at the end of inspiration?
    -10 cm H2O
  12. Pta
    Transairway pressure
  13. Transairway pressure (Pta)
    Is the pressure difference between the airway opening and the alveolus
  14. Transairway pressure equals...
    • Pta= Paw - Palv
    • the pressure gradient requried to produce airflow in the conductive airways
    • It represents the pressure that must be generated to overcome resistance to gas flow in the airways
  15. Transpulmonary Pressure
    The pressure difference between the alveolar space and the pleural space
  16. Transpulmonary pressure equals...
    PL = Palv - Ppl
  17. Transpulmonary pressure is the pressure requried to...
    maintain alveolar inflation
  18. Negative pressure ventilation
    Increse transpulmonary pressure during inspiration by decreasing intrapleural pressure
  19. Palv
    Alveolus pressure
  20. Positive pressure ventilation
    Increase transpulmonary pressure by increasing alveolus pressure by increasing pressure at the upper airway
  21. Pplateau
    An airway pressure measurement
  22. Transrespiratory pressure
    is the pressure difference between the airway opening and the body surface
  23. Ptr
    transrespiratory pressure
  24. Transrespiratory pressure is used to describe...
    the pressure requried to inflate the lungs and airways during positive pressure ventilation
  25. Transrespiratrory pressure has two components...
    • Transthoracic pressure
    • Transairway pressure
  26. Transthoracic pressure
    the pressure requried to overcome elastic recoil of the lungs and chest wall
  27. Transairway pressure
    The pressure requried to overcome airway resistance
  28. Accessory muscle of inspiration!
    • Scalene
    • Sternocleidomastoids
    • Pectoralis
    • Trapezius
  29. Accessory muscles of Expiration!
    • Rectus abdominus
    • External oblique
    • Internal oblique
    • Transverse abdominal
    • Serratus
    • Latissimus
  30. Negative Pressure Ventilation
    Attemps to mimic the function of the respiratory muscles to allow breathing through normal mechanics
  31. What is an example of a negative pressure ventilation?
    • Iron lung
    • Pneumosuit
    • chest cuirass
  32. The advantages of negative pressure ventilation!
    • The upper airway can be maintained without the use of an endotracheal tube or tracheotomy
    • Can talk and eat while being ventilated
    • Has fewer physiological disadvantages in patients with normal cardiovascualar function
  33. Positive pressure ventilation
    occurs when a mechanical ventilator is used to move air into the patient's lung by way of an endotracheal tube or positive pressure mask
  34. High frequency ventilation
    uses the above normal ventilating rates with below normal ventilating volumes
  35. There are three types of high frequency ventilation strategies...
    • High frequency positive pressure ventilation
    • high frequency jet ventilation
    • high frequency oscillatory ventilation
  36. High frequency positive pressure ventilation
    • Uses Respiratory rates of about 60 to 100 breaths/min
    • can be accomplished with a coventional positive pressure ventilator set at high rates and lower than normal tidal volumes
  37. High frequency jet ventilation
    • uses respiratory rates about 100 and 400 to 600 breaths/min
    • involves delivering pressurized jets of gas into the lungs at very high frequencies
  38. High frequency oscillatory ventilation
    • Uses respiratory rates into the thousands, up to about 4000 breath/min
    • used primarily in infants with respiratory distress and in adults or infants with open air leaks, such as bronchopleural fistulas
  39. Positive end expiratory pressure
    When PEEP is set, the ventilator prevents the patient from exhaling to zero
  40. What does positive end expiratory pressure (PEEP) do?
    • increases the volume of gas reamaining in the lungs at the end of normal exhalation
    • PEEP increases the functional residual capacity
  41. Manometer or pressure gauge
    A clinician can check on a ventilator for a reading of the pressure present at that moment
  42. Peak inspiratory pressure
    This is the highest pressure recorded at the end of inspiration
  43. The pressures measured during inspiration are the sum of two pressures...
    The pressure required to force the gas through the resistance of the airways (Pta) and the pressure of the gas volume as it fills the alveoli
  44. PIP is the sum of...
    Pta and Palv at the end of inspiration
  45. Plateau pressure
    Inflation hold or inspiratory pause
  46. The plateau pressure is measured after...
    • A breath has been delivered to the patient and before exhalation begins
    • Exhalation is prevented by the ventilator for a brief moment (0.5-1.5 seconds)
  47. If a baseline pressure is zero...
    This means no additional pressure is applied at the airway opening during expiration and before inspiration
  48. Compliance measurements are used...
    To describe the elastic forces that oppose lung inflation
  49. Compliace of the respiratory system is determined by...
    Measuring the change of volume that occurs when pressure is applied to that system
  50. Normal compliance in spontaneous breathing patients!
    50 to 170 mL/cm H2O
  51. Normal compliance in intubated patients!
    • Males: 40 to 50 mL/cm H2O, up to 100 ml/cm H2O
    • Females: 35 to 45 ml/cm H20, up to 100 ml/cm H2O
  52. Static compliance
    exhaled tidal volume/ plateau pressure- EEP
  53. Resistance
    Is a measurement of the fractional forces that must be overcome during breathing
  54. The resistance to airflow through the conductive airways (airway resistance) depends on...
    • the gas viscosity
    • the gas density
    • the length and diameter of the tube
    • the flow rate of gas through the tube
  55. How to calcuate resistance?
    RAW= Pta/flow
  56. Normal resistance values for a unintubated patient?
    AT 0.5L/s flow resistance is 0.6 to 2.4 cm     H20
  57. Normal resistance values for intubated patient!
    Approximately 6 cm H2O or higher
  58. Time constants
    • The length of time lung units requrie to fill and empty
    • The product of compliance and resistance
  59. Open loop Systems
    the operator sets a control (tidal volume) and the ventilator delivers that volume to the patient circuit.
  60. Why are open loop systems are called unitelligent systems?
    • Because the veentilator cannot be programmed to respond to changing conditions
    • If gas leaks out the patients circuit, an open loop cannot adjust its function to correct for the leakage
    • It simply delivers a set volume or output and does not measure or change it
  61. Closed loop systems
    are described as intelligent systems because they compare the set control variable to the measured control variable, which in turn allows the ventilator to respond to changes in the patients condition
  62. Electrically powered ventilators
    • Rely entirely on electricity.
    • The electrical source may be a standard electrical outlet
    • Help ensure a controlled pressure and gas flow to the patient
  63. Pneumatically powered Ventilators
    • Depend entirely on a compressed gas source for power
    • These machines use 50 psi gas source and have built in internal reducing valves so that the operating pressure is lower that the source pressure
    • Controls flow, volume delievery and inspiration and expiration function
  64. Basic elements of a patients circuit!
    • main inspiratory line
    • Adapter
    • Expiratory line
    • Expiratory valve
  65. Basic elements of a patients circuit
    Main inspiratory line
    Connects the ventilator output to the patient's airway adapter or connector
  66. Basic elements of a patients circuit
    Connects the main inspiratory line to the patient's airway
  67. Basic elements of a patients circuit
    Expiratory line
    Delivers expired gas from the patient to the exhalation valve
  68. Basic elements of a patients circuit
    Expiratory Valve
    Allows the release of exhaled gas from the expiratory line into the room air
  69. Pressure controlled breathing
    The ventilator maintains the same pressure waveform at the mouth regardless of changes in lung characteristics
  70. In pressure controlled breathing with changes in compliance and resistance...
    The volume and flow waveforms will vary
  71. Volume controlled breathing
    Ventilator volume delivery and volume waveform remain constant and are not affected by changes in lung charecteristics. Volume is measured
  72. In volume controlled breathing with changes in lung characteristics...
    the volume and flow remain unchanged, but the pressure waveform varies with changes in lung characteristics
  73. Time triggered ventilation
    • The breath begins when the ventilator has measured an elapsed amount of time
    • The ventilator controls the number of breaths delivered per minute
    • Control mode
    • Madatory breath because it is intiated by the ventilator
  74. Patients Triggered Ventilation
    • When a patients attempts to breath spontaneously during mechanical ventilation, amechanism must be available to measure the patient's effort to breath
    • When the ventilator detects changes in pressure, flow, or volume, a patient triggered breath occurs
  75. What is the maximum safety pressure limit? 
    • 10 cm H2O above the average peak inspiratory pressure
    • Reaching the maximun high pressure limit ends the inspiratory phase
  76. How much volume is loss in most ventilator circuits?
    About 2 to 3 mL of gas is lost to tubeing compressibility for every 1 cm H2O that is measured by the airway sensor
  77. Inflation hold or Inspiratory pause
    • Designed to maintain air in  the lungs at the end of inspiration, before the exhalation valve opens
    • The inspiratory pause occasionally is used to increase peripheral distrubition of gas and improve oxygenation
    • It increases the inspiratory time and reduces the expiratory time
  78. Expiration hold
    • End expiratory pause
    • The purpose of this manever is to measure pressure associated with air trapped in the lungs at the end of the expiration
  79. CPAP
    Involves the application of pressures above ambient throughout inspiration and expiration to improve oxygention in a spontaneously breathing patient
  80. CPAP has been used fro the treatment of a variety of disorders...
    • Postoperative atelectasis
    • Obstructive sleep apnea
  81. CPAP and PEEP help prevent...
    Early airway closure and alveolar collapse at the end of expiration by increasing the patients FRC, Which in turn allows for better oxygentation
  82. BiPAP
    • With bilevel positive airway pressure, the inspiratory positive airway pressure is higher than the expiratory positive airway pressure
    • Is patient triggered, pressure targeted, and flow or time cycled
  83. Pressure volume loops
    Can be used to monitor changes in lung compliance and airway resistance
  84. Hysteresis
    • CAn be thought of as a lagging of one of two associated phenomena
    • An example of hysteresis is the difference between the inspiratory and expiratory curves in a pressure volume loop for the lungs
Card Set
Mechanical Ventilation
test 1
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